Electronic Structure and Excited States of the Collision Reaction O(³P) + C₂H₄: A Multiconfigurational Perspective

Abstract

We present a study of the O­(3P) + C2H4 scattering reaction, a process that takes place in the interstellar medium and is of relevance in atmospheric chemistry as well. A comprehensive investigation of the electronic properties of the system has been carried out based on multiconfigurational ab initio CASSCF/CASPT2 calculations, using a robust and consistent active space that can deliver accurate potential energy surfaces in the key regions visited by the system. The paper discloses detailed description of the primary reaction pathways and the relevant singlet and triplet excited states at the CASSCF and CASPT2 level, including an accurate description of the critical configurations, such as minima and transition states. The chosen active space and the CASSCF/CASPT2 computational protocol are assessed against coupled-cluster calculations to further check the stability and reliability of the entire multiconfigurational procedure.

Adiabatic and Nonadiabatic Dynamics with Interacting Quantum Trajectories

“…Following the definition given in eq and expressing the electronic wavefunction as the ratio of the molecular and nuclear wavefunctions, from eq , the TDVP reads where S ( x , t ) is the phase of the nuclear wavefunction. It is easy to see that imposing the gauge condition A ( x , t ) = 0 yields an integral equation that defines S ( x , t ) in terms of the nuclear momentum fieldthat is, the first term on the right-hand side of eq .…”

“…where S(x, t) is the phase of the nuclear wavefunction. It is easy to see that imposing the gauge condition A(x, t) = 0 yields an integral equation that defines S(x, t) in terms of the nuclear momentum field 59 �that is, the first term on the right-hand side of eq 40.…”

Simulations of photoinduced processes with the exact factorization: State of the art and perspectives

“…In this case, the interaction potential V (r, R,t) depends on μ(r, R), the molecule electric dipole moment, and on E(t), the external time-dependent electric field. In some situations [154][155][156][157][158][159][160][161][162][163][164] , the relativistic correction due to the geometrydependent spin-orbit coupling ĤSOC (x, R) can be included in the system Hamiltonian, where the variable x = [r, σ] accounts for the electronic spin σ as well as for the electronic positions r.…”

The role of intersystem crossing in the reactive collision of S+(4S) with H2

“…More experimental studies can be found for larger systems, in particular by Casavecchia and coworkers who studied ISC in several reactions between atomic O( 3 P) with several unsaturated hydrocarbons 22 . The ISC in one of these reactions, O( 3 P)+C 2 H 4 , motivated numerous theoretical studies on the electronic stucture 23 and reaction dynamics studies using TSH 24,25 and NA-TST 26 . Although theory could qualitatively explain the experimental observation, it was not able to reproduce quantitatively the experimental branching ratio between products.…”